Preparation method of thermoplastic melamine glue impregnated decorative paper

Abstract

The invention relates to the technical field of decorative paper, in particular to a preparation method of thermoplastic melamine glue impregnated decorative paper, which comprises the following steps: step (1) pretreatment of base paper; (2) preparing thermoplastic melamine glue; and (3) gum dipping: dipping the pretreated base paper with thermoplastic melamine gum, drying, cooling, shearing, stacking, paving and hot-pressing to obtain the decorative paper dipped with the thermoplastic melamine gum. According to the scheme, a compound containing a flexible chain segment is introduced to a melamine molecule, and the ductility is improved by accurately controlling conditions such as the temperature, the pH value and the reaction time of a synthetic reaction; the modified nano silicon dioxide dispersion liquid is coated on the surface of the base paper, and the modified nano silicon dioxide is embedded in the base paper by utilizing gaps of the base paper, so that the interface bonding force between the filler and the resin is improved, the filler can play a better role, and the overall performance of the resin adhesive is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of decorative papers, and particularly to a preparation method of a thermoplastic melamine glue-impregnated decorative paper. Background Art

[0002] At present, the preparation methods of melamine-impregnated decorative papers mainly include process steps such as glue preparation, impregnation, drying, and cooling. In terms of glue preparation, melamine formaldehyde resin is usually prepared by reacting melamine with formaldehyde, or urea formaldehyde resin is prepared by reacting urea with formaldehyde, or both are used in combination. CN107164992B discloses a low-formaldehyde melamine-impregnated decorative paper and its preparation method, which includes steps such as the preparation of urea formaldehyde glue resin, the preparation of melamine glue resin, primary dipping, and secondary dipping. By controlling the raw material ratio and process parameters, the formaldehyde release amount of the obtained impregnated paper can be effectively controlled at ≤0.3 mg / L.

[0003] In terms of the impregnation process, CN107724172A discloses a new impregnated paper production process. In this process, through two impregnations, first, the lower-cost urea formaldehyde resin is used for the first impregnation, and then the higher-cost but better-performing melamine resin is used for the second impregnation, which reduces the manufacturing cost while ensuring the surface performance of the impregnated paper. CN107354812A discloses a production process of a high-gloss and low-cost impregnated paper, including steps such as first dipping, first drying, spraying, coating, second drying, and cutting. Through the improvement of the impregnation process, an oily feeling can be produced on the surface of the floor or furniture after lamination, and the surface gloss has been greatly improved.

[0004] In order to solve the problem of high formaldehyde release amount of melamine-impregnated papers, CN117385671A proposes a preparation method of a low-formaldehyde-release melamine-impregnated paper, which is made into a resin by modifying low-molar urea formaldehyde resin with melamine, adding phenylmelamine and formaldehyde, and cooperating with the addition of a formaldehyde scavenger. At the same time, indicators such as the temperature, time, pH value, and addition amount of raw materials in the impregnated paper preparation process are controlled. CN108130796A discloses a preparation method of a decorative paper for purifying formaldehyde. In this method, an impregnating adhesive solution is obtained by mixing urea formaldehyde resin with modified starch, water-soluble chitosan, etc., and is dried in a mixed atmosphere of dry air and ammonia, so that the obtained decorative paper for decoration has good ability to capture and remove formaldehyde.

[0005] However, the melamine-impregnated decorative papers in the prior art generally have the problem of insufficient ductility. They are prone to cracking when bent or stretched, and cannot meet the application requirements of special packaging or decoration fields for surface materials with a certain deformation ability. This is mainly because the network structure formed after the traditional melamine-urea formaldehyde resin is cured is too rigid and lacks sufficient flexibility. Although CN117385671A mentions adding isocyanate during the softening process of melamine resin to improve toughness, the ductility problem of the impregnated paper in specific application scenarios has not been completely solved. Summary of the Invention

[0006] To solve the technical problem that the traditional melamine glue-impregnated decorative paper lacks ductility, is prone to cracking when bent or stretched, and cannot meet the application requirements of special packaging or decoration fields for surface materials with a certain deformation ability, and to achieve the technical effects of improving the ductility of the impregnated decorative paper, improving the impregnation effect, optimizing the production process, and realizing special functions, the present invention provides a preparation method for a thermoplastic melamine glue-impregnated decorative paper.

[0007] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0008] A preparation method for a thermoplastic melamine glue-impregnated decorative paper, comprising the following steps:

[0009] Step (1) Base paper pretreatment: Coating a modified nano-silica dispersion liquid on the surface of the base paper, with a coating amount of 8-12 g / m 2 , and then drying under the conditions of 0.001~0.02 MPa and a temperature of 40-50 °C to obtain a pretreated base paper;

[0010] Step (2) Preparation of thermoplastic melamine glue: By parts, mix 1200-1400 parts of formaldehyde with 90-110 parts of ammonia water, adjust the pH to 8.8-9.2. After the reaction temperature rises to 55-65 °C, add 180-220 parts of melamine, stir for 10 minutes, then add 380-420 parts of urea, heat to 83-90 °C, keep warm and evaporate until the mass percentage of water is 20%~30%, cool to 60 °C and add 70-90 parts of diethylene glycol, continue to cool to 30-40 °C, and then add 20%~30% of the total mass of acrylic resin, stir evenly to obtain thermoplastic melamine glue; it should be noted that in the chemical formula, "1200-1400 parts of formaldehyde" refers to the mass parts of 37% formaldehyde aqueous solution (formalin), rather than pure formaldehyde gas;

[0011] Step (3) Glue impregnation: Impregnate the pretreated base paper with thermoplastic melamine glue, dry, cool, cut, stack, lay, and hot press to obtain a thermoplastic melamine glue-impregnated decorative paper.

[0012] From a group perspective, melamine is formed by alternating connection of three carbon atoms and three nitrogen atoms to form a six-membered ring, and each carbon atom is also connected to an amino group respectively. The three carbon atoms and three nitrogen atoms are connected by covalent bonds in the form of alternating single and double bonds to form a six-membered heterocyclic ring, and this six-membered heterocyclic ring structure endows melamine with certain stability and special physical and chemical properties. Melamine resin is formed by the polycondensation of melamine and formaldehyde, and there is a triazine ring structure in the molecule. This structure has high bond energy and symmetry, enabling it to remain stable within a certain temperature range and not easily undergo chain breakage or rearrangement of the molecular chain. During the curing process, melamine resin forms a highly crosslinked three-dimensional network structure. For the above reasons, the formula is adjusted before curing to ensure that the melamine resin has ductility.

[0013] This solution mainly improves the ductility by step (2), introducing a compound containing a flexible chain segment onto the melamine molecule and precisely controlling conditions such as the temperature, pH value, and reaction time of the synthesis reaction.

[0014] Secondly, in this solution, the modified nano-silica dispersion is coated on the surface of the base paper, and the modified nano-silica is embedded therein by utilizing the gaps of the base paper, which can improve the interfacial bonding force between the filler and the resin, enabling the filler to play a better role, thereby improving the overall performance of the resin glue, including ductility. Among them, the pressure conditions in this solution can evaporate water faster and embed the modified nano-silica into the gaps of the base paper fibers, which can form hydrogen bonds or covalent bonds with the hydroxyl groups of the fiber paper, enhancing the tensile strength and folding endurance of the base paper, and can also fill the micropores between the fibers, reducing stress concentration points and inhibiting crack propagation. Moreover, the organic chain segments of the modified nano-silica form an interpenetrating network with the subsequently impregnated thermoplastic melamine glue, which can improve the interfacial shear strength. After the modified nano-silica is coated as a pre-coating, it can balance the surface energy difference between the base paper and the thermoplastic melamine glue, reducing the "resin rejection" phenomenon and the volatility of the sizing amount during subsequent sizing.

[0015] Preferably, in step (1), the modified nano-silica dispersion includes: 5% - 10% of modified nano-silica by mass percentage, 1% - 3% of hydroxyethyl acrylate, 1% - 2% of acrylic acid, and the rest is water.

[0016] Preferably, in the modified nano-silica dispersion, the modified nano-silica is acrylic acid grafted nano-silica.

[0017] The acrylic grafted nano-silica dispersion can be prepared by the following method: By weight, 1 part of nano-silica is dispersed in 30 - 35 parts of deionized water. After ultrasonic treatment, 0.3 - 0.9 part of vinyltrimethoxysilane is added, and the pH of the system is adjusted to 9 - 11 with ammonia water. Stirring reaction is carried out at 80 - 85 °C for 5 - 8 h, and after drying, silane-modified nano-silica is obtained. Then, an aqueous solution containing 5% - 10% by mass of silane-modified nano-silica, 1% - 3% of hydroxyethyl acrylate, and 1% - 2% of acrylic acid is prepared, 0.01 - 0.1 part of potassium persulfate initiator is added, and reaction is carried out at 80 - 90 °C for 1 - 2 h to obtain the modified nano-silica dispersion.

[0018] Preferably, in step (1), the water content percentage of the pretreated base paper is 6% - 8%.

[0019] Excessive moisture will dilute the melamine glue, resulting in insufficient curing and defects such as bubbles and blisters during hot pressing; too low moisture will increase the brittleness of the base paper and it is easy to break during sizing.

[0020] Preferably, the density of the thermoplastic melamine glue is 1.0 - 1.3 g / cm 3 .

[0021] Preferably, in step (3), the process of impregnating the pretreated base paper with the thermoplastic melamine glue is as follows: The pretreated base paper first passes through the back coating roller, then the excess glue is wiped off with a metering roller, passes through a drying oven, the drying temperature is 110 - 135 °C, so that the water content of the impregnated paper is 12% - 15%, the sizing amount is 60 - 70 g / cm², and then it is cooled.

[0022] Preferably, before wiping off the excess glue with the metering roller, air is discharged by a breathing roller with a curvature to filter the liquid.

[0023] Preferably, in step (3), the drying method is drying with a seven-section oven. The temperature of the first section of the oven is 110 °C, the temperature of the second section of the oven is 125 °C, the temperature of the third section of the oven is 135 °C, the temperature of the fourth section of the oven is 130 °C, the temperature of the fifth section of the oven is 130 °C, the temperature of the sixth section of the oven is 130 °C, and the temperature of the seventh section of the oven is 120 °C.

[0024] Preferably, in step (3), the acrylic resin is a hydroxyacrylate-silicone copolymer.

[0025] Preferably, in step (3), the cooling method is to cool by blowing natural cold air through the oven, and then cool to a paper surface temperature of 25 - 30 °C by means of roller water cooling.

[0026] The impregnated paper prepared by this solution for the special packaging or decoration field, after special design, can meet the requirements of the product for ductility to a certain extent, is not easy to break when bent or stretched, and can adapt to some applications that require the surface material to have a certain deformation ability.

[0027] Compared with the prior art, the advantages of this solution are as follows:

[0028] 1. In this solution, a compound containing a flexible segment is introduced into the melamine molecule, and by precisely controlling conditions such as the temperature, pH value, and reaction time of the synthesis reaction, the ductility is improved.

[0029] 2. In this solution, the modified nano-silica dispersion is coated on the surface of the base paper, and by using the gaps of the base paper, the modified nano-silica is embedded therein, which can improve the interfacial bonding force between the filler and the resin, enable the filler to play a better role, and thus improve the overall performance of the resin glue. Specific implementation mode

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] In the following examples and comparative examples, the preparation method of the used modified nano-silica dispersion is as follows: The acrylic acid grafted nano-silica dispersion can be prepared by the following method: By weight, 1 part of nano-silica is dispersed in 30 parts of deionized water, after ultrasonic treatment, 0.5 part of vinyltrimethoxysilane is added, the pH of the system is adjusted to 10 with ammonia water, and the reaction is stirred at 83 °C for 6 h, and after drying, silane-modified nano-silica is obtained; then an aqueous solution containing 8% of silane-modified nano-silica, 2% of hydroxyethyl acrylate and 1.5% of acrylic acid by mass fraction is prepared, 0.05 part of potassium persulfate initiator is added, and the reaction is carried out at 85 °C for 1.5 h to obtain the modified nano-silica dispersion.

[0032] Example 1

[0033] A preparation method of a thermoplastic melamine glue-impregnated decorative paper includes the following steps:

[0034] Step (1) Base paper pretreatment: Coat the modified nano-silica dispersion on the surface of the base paper, with a coating amount of 10 g / m 2 , and then dry under the conditions of 0.005 MPa and a temperature of 45 °C to obtain a pretreated base paper, and the water content percentage of the pretreated base paper is 7%;

[0035] Step (2) Preparation of thermoplastic melamine glue: By parts, mix 1300 parts of 37% aqueous formaldehyde solution with 100 parts of ammonia water, adjust the pH to 9. After the reaction temperature rises to 60 °C, add 200 parts of melamine, stir for 10 minutes, then add 400 parts of urea, heat to 85 °C, keep warm and evaporate until the mass percentage of water is 25%. When the temperature drops to 60 °C, add 80 parts of diethylene glycol, continue to cool to 35 °C, and then add 25% of the total mass of hydroxyacrylate-silicone copolymer. After stirring evenly, obtain thermoplastic melamine glue with a density of 1.2 g / cm 3 ;

[0036] Step (3) Glue dipping: Dip the pretreated base paper with the thermoplastic melamine glue. The pretreated base paper first passes through the back coating roller, and the air is discharged by the breathing roller with an arc to filter the liquid. Then, use the metering roller to wipe off the excess glue, and dry it through a seven-section oven. The temperature of the first section of the oven is 110 °C, the temperature of the second section of the oven is 125 °C, the temperature of the third section of the oven is 135 °C, the temperature of the fourth section of the oven is 130 °C, the temperature of the fifth section of the oven is 130 °C, the temperature of the sixth section of the oven is 130 °C, and the temperature of the seventh section of the oven is 120 °C, so that the water content of the impregnated paper is 13% and the sizing amount is 65 g / cm². Cool it by blowing natural cold air through the oven, and then cool it to the paper surface temperature of 25 °C by the roller water cooling method, shear, stack, lay, and hot press to obtain the thermoplastic melamine glue impregnated decorative paper.

[0037] Example 2

[0038] A preparation method of thermoplastic melamine glue impregnated decorative paper, comprising the following steps:

[0039] Step (1) Base paper pretreatment: Coat the surface of the base paper with a modified nano-silica dispersion liquid, with a coating amount of 9 g / m 2 , and then dry it under the conditions of 0.008 MPa and 45 °C to obtain the pretreated base paper, and the water content percentage of the pretreated base paper is 7%;

[0040] Step (2) Preparation of thermoplastic melamine glue: By parts, mix 1200 parts of 37% aqueous formaldehyde solution with 110 parts of ammonia water, adjust the pH to 9. After the reaction temperature rises to 60 °C, add 200 parts of melamine, stir for 10 minutes, then add 390 parts of urea, heat to 88 °C, keep warm and evaporate until the mass percentage of water is 28%. When the temperature drops to 60 °C, add 75 parts of diethylene glycol, continue to cool to 35 °C, and then add 25% of the total mass of hydroxyacrylate-silicone copolymer. After stirring evenly, obtain thermoplastic melamine glue with a density of 1.2 g / cm 3 ;

[0041] Step (3) Glue impregnation: Impregnate the pretreated base paper with thermoplastic melamine glue. The pretreated base paper first passes through the back coating roller, and a breathing roller with an arc is used to filter out air from the filtrate. Then, a metering roller is used to wipe off the excess glue. It is dried through a seven-section oven. The temperature of the first section of the oven is 110°C, the temperature of the second section of the oven is 125°C, the temperature of the third section of the oven is 135°C, the temperature of the fourth section of the oven is 130°C, the temperature of the fifth section of the oven is 130°C, the temperature of the sixth section of the oven is 130°C, and the temperature of the seventh section of the oven is 120°C, so that the water content of the impregnated paper is 13%, and the glue application amount is 65 g / cm². It is cooled by blowing natural cold air through the oven, and then cooled to a paper surface temperature of 28°C by means of roller water cooling, sheared, stacked, paved, and hot-pressed to obtain the thermoplastic melamine glue-impregnated decorative paper.

[0042] Example 3

[0043] A preparation method of a thermoplastic melamine glue-impregnated decorative paper, comprising the following steps:

[0044] Step (1) Base paper pretreatment: Coating a modified nano-silica dispersion liquid on the surface of the base paper, with a coating amount of 11 g / m 2 , and then drying under the conditions of 0.01 MPa and a temperature of 40 - 50°C to obtain the pretreated base paper, and the water content percentage of the pretreated base paper is 6% - 8%;

[0045] Step (2) Preparation of thermoplastic melamine glue: By parts, mix 1400 parts of 37% formaldehyde aqueous solution with 90 parts of ammonia water, adjust the pH to 9.0. When the reaction temperature rises to 58°C, add 190 parts of melamine, stir for 10 minutes, then add 390 parts of urea, heat to 88°C, keep warm and evaporate until the water mass percentage is 26%, cool to 60°C and add 86 parts of diethylene glycol, continue to cool to 35°C, and then add 26% of the total mass of the hydroxyacrylate-silicone copolymer. After stirring evenly, obtain a thermoplastic melamine glue with a density of 1.2 g / cm 3 ;

[0046] Step (3) Glue impregnation: Impregnate the pretreated base paper with thermoplastic melamine glue. The pretreated base paper first passes through the back coating roller, and a breathing roller with an arc is used to filter out air from the filtrate. Then, a metering roller is used to wipe off the excess glue. It is dried through a seven-section oven. The temperature of the first section of the oven is 110°C, the temperature of the second section of the oven is 125°C, the temperature of the third section of the oven is 135°C, the temperature of the fourth section of the oven is 130°C, the temperature of the fifth section of the oven is 130°C, the temperature of the sixth section of the oven is 130°C, and the temperature of the seventh section of the oven is 120°C, so that the water content of the impregnated paper is 14%, and the glue application amount is 66 g / cm². It is cooled by blowing natural cold air through the oven, and then cooled to a paper surface temperature of 28°C by means of roller water cooling, sheared, stacked, paved, and hot-pressed to obtain the thermoplastic melamine glue-impregnated decorative paper.

[0047] Example 4

[0048] A preparation method of a thermoplastic melamine glue-impregnated decorative paper, comprising the following steps:

[0049] Step (1) Base paper pretreatment: Coating a modified nano-silica dispersion on the surface of the base paper, with a coating amount of 9 g / m 2 , and then drying under the conditions of 0.012 MPa and a temperature of 45 °C to obtain a pretreated base paper, and the water content percentage of the pretreated base paper is 7%;

[0050] Step (2) Preparation of thermoplastic melamine glue: By parts, mixing 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjusting the pH to 9.0. When the reaction temperature rises to 55-65 °C, adding 190 parts of melamine, stirring for 10 minutes, then adding 410 parts of urea, heating to 88 °C, keeping warm and evaporating until the water mass percentage is 25%, cooling to 60 °C and adding 80 parts of diethylene glycol, continuing to cool to 38 °C, and then adding 26% of the total mass of hydroxyacrylate-silicone copolymer, and stirring evenly to obtain a thermoplastic melamine glue with a density of 1.2 g / cm 3 ;

[0051] Step (3) Glue impregnation: Impregnating the pretreated base paper with the thermoplastic melamine glue. The pretreated base paper first passes through a back coating roller, and the breathing roller with an arc is used to filter out air from the filtrate, then the excess glue is wiped off with a metering roller, dried through an oven to make the water content of the impregnated paper 13%, the sizing amount is 65 g / cm², cooled by blowing natural cold air through the oven, and then cooled to the paper surface temperature of 28 °C by means of roller water cooling, sheared, stacked, paved, and hot-pressed to obtain the thermoplastic melamine glue-impregnated decorative paper.

[0052] Example 5

[0053] A preparation method of a thermoplastic melamine glue-impregnated decorative paper, comprising the following steps:

[0054] Step (1) Base paper pretreatment: Coating a modified nano-silica dispersion on the surface of the base paper, with a coating amount of 10 g / m 2 , and then drying under the conditions of 0.005 MPa and a temperature of 45 °C to obtain a pretreated base paper, and the water content percentage of the pretreated base paper is 7%;

[0055] Step (2) Preparation of thermoplastic melamine glue: By parts, mix 1300 parts of 37% aqueous formaldehyde solution with 100 parts of ammonia water, adjust the pH to 9. After the reaction temperature rises to 60 °C, add 200 parts of melamine, stir for 10 minutes, then add 400 parts of urea, heat to 85 °C, keep warm and evaporate until the mass percentage of water is 25%. When the temperature drops to 60 °C, add 80 parts of diethylene glycol, continue to cool to 35 °C, and then add 25% of the total mass of hydroxyacrylate-silicone copolymer. After stirring evenly, obtain thermoplastic melamine glue with a density of 1.2 g / cm 3 of thermoplastic melamine glue;

[0056] Step (3) Glue dipping: Dip the pretreated base paper with the thermoplastic melamine glue. The pretreated base paper first passes through the back coating roller, and the air is discharged by the breathing roller with an arc to filter the liquid. Then, use the metering roller to wipe off the excess glue, and dry it through a seven-section oven. The temperature of the first section of the oven is 110 °C, the temperature of the second section of the oven is 125 °C, the temperature of the third section of the oven is 135 °C, the temperature of the fourth section of the oven is 130 °C, the temperature of the fifth section of the oven is 130 °C, the temperature of the sixth section of the oven is 130 °C, and the temperature of the seventh section of the oven is 120 °C, so that the water content of the impregnated paper is 13%, the sizing amount is 65 g / cm², cool it to the paper surface temperature of 25 °C by blowing natural cold air through the oven, shear, stack, pave, and hot press to obtain the thermoplastic melamine glue impregnated decorative paper.

[0057] Comparative Example 1

[0058] The difference from Example 1 is that the nano-silica dispersion liquid is not coated:

[0059] A preparation method of thermoplastic melamine glue impregnated decorative paper, comprising the following steps:

[0060] Step (1) Preparation of thermoplastic melamine glue: By parts, mix 1300 parts of 37% aqueous formaldehyde solution with 100 parts of ammonia water, adjust the pH to 9. After the reaction temperature rises to 60 °C, add 200 parts of melamine, stir for 10 minutes, then add 400 parts of urea, heat to 85 °C, keep warm and evaporate until the mass percentage of water is 25%. When the temperature drops to 60 °C, add 80 parts of diethylene glycol, continue to cool to 35 °C, and then add 25% of the total mass of hydroxyacrylate-silicone copolymer. After stirring evenly, obtain thermoplastic melamine glue with a density of 1.2 g / cm 3 of thermoplastic melamine glue;

[0061] Step (2) Impregnation: Impregnate the base paper with thermoplastic melamine glue. The pretreated base paper first passes through the back coating roller, and the air is discharged by the breathing roller with an arc to filter the liquid. Then, the excess glue is wiped off by the metering roller and dried through a seven-section oven. The temperature of the first section of the oven is 110 °C, the temperature of the second section of the oven is 125 °C, the temperature of the third section of the oven is 135 °C, the temperature of the fourth section of the oven is 130 °C, the temperature of the fifth section of the oven is 130 °C, the temperature of the sixth section of the oven is 130 °C, and the temperature of the seventh section of the oven is 120 °C, so that the water content of the impregnated paper is 13%, the glue application amount is 65 g / cm², and it is cooled by blowing natural cold air through the oven. Then, it is cooled to the paper surface temperature of 25 °C by the roller water cooling method, sheared, stacked, paved, and hot-pressed to obtain the thermoplastic melamine glue-impregnated decorative paper.

[0062] Comparative Example 2

[0063] The difference from Example 1 is that a nano-silica dispersion liquid is coated:

[0064] A preparation method of a thermoplastic melamine glue-impregnated decorative paper, comprising the following steps:

[0065] Step (1) Base paper pretreatment: Coat a nano-silica dispersion liquid on the surface of the base paper, with a coating amount of 10 g / m 2 , and then dry it under the conditions of 0.005 MPa and a temperature of 45 °C to obtain a pretreated base paper, and the water content percentage of the pretreated base paper is 7%;

[0066] Step (2) Preparation of thermoplastic melamine glue: By parts, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9. When the reaction temperature rises to 60 °C, add 200 parts of melamine, stir for 10 minutes, then add 400 parts of urea, heat to 85 °C, keep warm and evaporate until the water mass percentage is 25%, cool to 60 °C and add 80 parts of diethylene glycol, continue to cool to 35 °C, and then add 25% of the total mass of hydroxyacrylate-silicone copolymer, and stir evenly to obtain a thermoplastic melamine glue with a density of 1.2 g / cm 3 ;

[0067] Step (3) Glue impregnation: The pretreated base paper is impregnated with thermoplastic melamine glue. The impregnated paper first passes through the back coating roller, and the air is discharged by the breathing roller with an arc to filter the liquid. Then, the excess glue is wiped off by the metering roller and dried through a seven-section oven. The temperature of the first section of the oven is 110 °C, the temperature of the second section of the oven is 125 °C, the temperature of the third section of the oven is 135 °C, the temperature of the fourth section of the oven is 130 °C, the temperature of the fifth section of the oven is 130 °C, the temperature of the sixth section of the oven is 130 °C, and the temperature of the seventh section of the oven is 120 °C, so that the water content of the impregnated paper is 13%, the glue application amount is 65 g / cm², and it is cooled by blowing natural cold air through the oven, and then cooled to the paper surface temperature of 25 °C by the roller water cooling method, sheared, stacked, paved, and hot-pressed to obtain the thermoplastic melamine glue-impregnated decorative paper.

[0068] Comparative Example 3

[0069] It is different from Example 1 in that conventional melamine glue is directly coated:

[0070] A preparation method of a thermoplastic melamine glue-impregnated decorative paper includes the following steps:

[0071] Step (1) Base paper pretreatment: A modified nano-silica dispersion liquid is coated on the surface of the base paper, and the coating amount is 10 g / m 2 , and then dried under the conditions of 0.005 MPa and a temperature of 45 °C to obtain the pretreated base paper, and the water content percentage of the pretreated base paper is 7%;

[0072] Step (2) Glue impregnation: The pretreated base paper is impregnated with melamine glue. The impregnated paper first passes through the back coating roller, and the air is discharged by the breathing roller with an arc to filter the liquid. Then, the excess glue is wiped off by the metering roller and dried through a seven-section oven. The temperature of the first section of the oven is 110 °C, the temperature of the second section of the oven is 125 °C, the temperature of the third section of the oven is 135 °C, the temperature of the fourth section of the oven is 130 °C, the temperature of the fifth section of the oven is 130 °C, the temperature of the sixth section of the oven is 130 °C, and the temperature of the seventh section of the oven is 120 °C, so that the water content of the impregnated paper is 13%, the glue application amount is 65 g / cm², and it is cooled by blowing natural cold air through the oven, and then cooled to the paper surface temperature of 25 °C by the roller water cooling method, sheared, stacked, paved, and hot-pressed to obtain the thermoplastic melamine glue-impregnated decorative paper.

[0073] Comparative Example 4

[0074] The difference from Example 1 is that after coating the modified nano-silica dispersion liquid, it is not treated under low pressure:

[0075] A preparation method of a thermoplastic melamine glue-impregnated decorative paper includes the following steps:

[0076] Step (1) Base paper pretreatment: A modified nano-silica dispersion liquid is coated on the surface of the base paper, and the coating amount is 10 g / m 2, dry at a temperature of 45°C to obtain a pretreated base paper with a water content percentage of 7%;

[0077] Step (2) Preparation of thermoplastic melamine glue: By parts, mix 1300 parts of 37% aqueous formaldehyde solution with 100 parts of ammonia water, adjust the pH to 9. After the reaction temperature rises to 60°C, add 200 parts of melamine, stir for 10 minutes, then add 400 parts of urea, heat to 85°C, keep warm and evaporate until the water mass percentage is 25%, cool to 60°C and add 80 parts of diethylene glycol, continue to cool to 35°C, and then add 25% of the total mass of hydroxyacrylate-silicone copolymer. After stirring evenly, obtain a thermoplastic melamine glue with a density of 1.2 g / cm 3 ;

[0078] Step (3) Glue impregnation: Impregnate the pretreated base paper with thermoplastic melamine glue. The impregnated paper first passes through a back coating roller, and a breathing roller with an arc is used to filter out air from the filtrate. Then, a metering roller is used to wipe off the excess glue, and it is dried through a seven-section oven. The temperature of the first section of the oven is 110°C, the temperature of the second section of the oven is 125°C, the temperature of the third section of the oven is 135°C, the temperature of the fourth section of the oven is 130°C, the temperature of the fifth section of the oven is 130°C, the temperature of the sixth section of the oven is 130°C, and the temperature of the seventh section of the oven is 120°C, so that the water content of the impregnated paper is 13%, the glue application amount is 65 g / cm², it is cooled by blowing natural cold air through the oven, and then cooled to a paper surface temperature of 25°C by means of roller water cooling, sheared, stacked, paved, and hot-pressed to obtain a thermoplastic melamine glue-impregnated decorative paper.

[0079] Comparative Example 5

[0080] The difference from Example 1 is that the moisture content of the pretreated base paper exceeds the standard, being 9%:

[0081] A method for preparing a thermoplastic melamine glue-impregnated decorative paper, comprising the following steps:

[0082] Step (1) Base paper pretreatment: Coat a modified nano-silica dispersion liquid on the surface of the base paper, with a coating amount of 10 g / m 2 , and then dry under the conditions of 0.005 MPa and a temperature of 45°C to obtain a pretreated base paper with a water content percentage of 9%;

[0083] Step (2) Preparation of thermoplastic melamine glue: By parts, mix 1300 parts of 37% aqueous formaldehyde solution with 100 parts of ammonia water, adjust the pH to 9. After the reaction temperature rises to 60 °C, add 200 parts of melamine, stir for 10 minutes, then add 400 parts of urea, heat to 85 °C, keep warm and evaporate until the mass percentage of water is 25%, cool to 60 °C and add 80 parts of diethylene glycol, continue to cool to 35 °C, and then add 25% of the total mass of hydroxyacrylate-silicone copolymer. After stirring evenly, obtain thermoplastic melamine glue with a density of 1.2 g / cm 3 of thermoplastic melamine glue;

[0084] Step (3) Glue dipping: Dip the pretreated base paper with thermoplastic melamine glue. The dipped paper first passes through a back coating roller, and the breathing roller with an arc filters out air, then uses a metering roller to wipe off the excess glue, and dries it through a seven-section oven. The temperature of the first section of the oven is 110 °C, the temperature of the second section of the oven is 125 °C, the temperature of the third section of the oven is 135 °C, the temperature of the fourth section of the oven is 130 °C, the temperature of the fifth section of the oven is 130 °C, the temperature of the sixth section of the oven is 130 °C, and the temperature of the seventh section of the oven is 120 °C, so that the water content of the dipped paper is 13%, the sizing amount is 65 g / cm², cool it by blowing natural cold air through the oven, and then cool it to the paper surface temperature of 25 °C by the roller water cooling method, shear, stack, lay, and hot press to obtain thermoplastic melamine glue dipped decorative paper.

[0085] Comparative Example 6

[0086] The difference from Example 1 is that in the preparation process of thermoplastic melamine glue, acrylic resin is not added:

[0087] A preparation method of thermoplastic melamine glue dipped decorative paper, comprising the following steps:

[0088] Step (1) Base paper pretreatment: Coating the surface of the base paper with a modified nano-silica dispersion liquid, the coating amount is 10 g / m 2 , and then dry it under the conditions of 0.005 MPa and a temperature of 45 °C to obtain a pretreated base paper, and the water content percentage of the pretreated base paper is 7%;

[0089] Step (2) Preparation of thermoplastic melamine glue: By parts, mix 1300 parts of 37% aqueous formaldehyde solution with 100 parts of ammonia water, adjust the pH to 9. After the reaction temperature rises to 60 °C, add 200 parts of melamine, stir for 10 minutes, then add 400 parts of urea, heat to 85 °C, keep warm and evaporate until the mass percentage of water is 25%, cool to 60 °C and add 80 parts of diethylene glycol, continue to cool to 35 °C, and stir evenly to obtain thermoplastic melamine glue with a density of 1.2 g / cm 3 of thermoplastic melamine glue;

[0090] Step (3) Impregnation: Impregnate the pretreated base paper with thermoplastic melamine glue. The impregnated paper first passes through a back coating roller, and a breathing roller with a curvature is used to drain air from the filtrate. Then, a metering roller is used to wipe off the excess glue, and it is dried through a seven-section oven. The temperature of the first section of the oven is 110°C, the temperature of the second section of the oven is 125°C, the temperature of the third section of the oven is 135°C, the temperature of the fourth section of the oven is 130°C, the temperature of the fifth section of the oven is 130°C, the temperature of the sixth section of the oven is 130°C, and the temperature of the seventh section of the oven is 120°C, so that the water content of the impregnated paper is 13% and the glue application amount is 65 g / cm². It is cooled by blowing natural cold air through the oven, and then cooled to a paper surface temperature of 25°C by means of roller water cooling, sheared, stacked, paved, and hot-pressed to obtain the thermoplastic melamine glue-impregnated decorative paper.

[0091] Comparative Example 7

[0092] The difference from Example 1 is that the addition amount of acrylic resin is excessive:

[0093] A preparation method of a thermoplastic melamine glue-impregnated decorative paper, comprising the following steps:

[0094] Step (1) Base paper pretreatment: Coat a modified nano-silica dispersion liquid on the surface of the base paper, with a coating amount of 10 g / m 2 , and then dry it under the conditions of 0.005 MPa and a temperature of 45°C to obtain a pretreated base paper, and the water content percentage of the pretreated base paper is 7%;

[0095] Step (2) Preparation of thermoplastic melamine glue: By parts, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9. When the reaction temperature rises to 60°C, add 200 parts of melamine, stir for 10 minutes, then add 400 parts of urea, heat to 85°C, keep warm and evaporate until the water mass percentage is 25%, cool to 60°C and add 80 parts of diethylene glycol, continue to cool to 35°C, and then add 40% of the total mass of hydroxyacrylate-silicone copolymer, and stir evenly to obtain a thermoplastic melamine glue with a density of 1.2 g / cm 3 ;

[0096] Step (3) Impregnation: Impregnate the pretreated base paper with thermoplastic melamine glue. The impregnated paper first passes through the back coating roller, and the air is discharged by the breathing roller with an arc to filter the liquid. Then, the excess glue is wiped off with a metering roller and dried through a seven-section oven. The temperature of the first section of the oven is 110°C, the temperature of the second section of the oven is 125°C, the temperature of the third section of the oven is 135°C, the temperature of the fourth section of the oven is 130°C, the temperature of the fifth section of the oven is 130°C, the temperature of the sixth section of the oven is 130°C, and the temperature of the seventh section of the oven is 120°C, so that the water content of the impregnated paper is 13% and the glue application amount is 65 g / cm². It is cooled by blowing natural cold air through the oven, and then cooled to the paper surface temperature of 25°C by the roller water cooling method, sheared, stacked, paved, and hot-pressed to obtain the thermoplastic melamine glue impregnated decorative paper.

[0097] Comparative Example 8

[0098] The difference from Example 1 is that in the preparation process of the thermoplastic melamine glue, the material addition order is different:

[0099] A preparation method of a thermoplastic melamine glue impregnated decorative paper, comprising the following steps:

[0100] Step (1) Base paper pretreatment: Coating a modified nano-silica dispersion liquid on the surface of the base paper, with a coating amount of 10 g / m 2 , and then drying under the conditions of 0.005 MPa and a temperature of 45°C to obtain a pretreated base paper, and the water content percentage of the pretreated base paper is 7%;

[0101] Step (2) Preparation of thermoplastic melamine glue: By parts, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9. When the reaction temperature rises to 60°C, add 80 parts of diethylene glycol, then add 200 parts of melamine, stir for 10 minutes, then add 400 parts of urea, heat to 85°C, keep warm and evaporate until the water mass percentage is 25%, continue to cool to 35°C, and then add 25% of the total mass of hydroxyacrylate-silicone copolymer, and stir evenly to obtain a thermoplastic melamine glue with a density of 1.2 g / cm 3 ;

[0102] Step (3) Impregnation: The pretreated base paper is impregnated with a thermoplastic melamine glue. The impregnated paper first passes through a backcoating roller, and a breathing roller with a curvature is used to drain air from the filtrate. Then, a metering roller is used to wipe off the excess glue. It is dried through a seven-section oven. The temperature of the first section of the oven is 110°C, the temperature of the second section of the oven is 125°C, the temperature of the third section of the oven is 135°C, the temperature of the fourth section of the oven is 130°C, the temperature of the fifth section of the oven is 130°C, the temperature of the sixth section of the oven is 130°C, and the temperature of the seventh section of the oven is 120°C, so that the water content of the impregnated paper is 13%, and the glue application amount is 65 g / cm². It is cooled by blowing natural cold air through the oven, and then cooled to a paper surface temperature of 25°C by a roller water cooling method, sheared, stacked, paved, and hot-pressed to obtain a thermoplastic melamine glue-impregnated decorative paper.

[0103] Comparative Example 9

[0104] The difference from Example 1 lies in that during the preparation process of the thermoplastic melamine glue, the temperature control is different:

[0105] A preparation method of a thermoplastic melamine glue-impregnated decorative paper, comprising the following steps:

[0106] Step (1) Base paper pretreatment: A modified nano-silica dispersion liquid is coated on the surface of the base paper, and the coating amount is 10 g / m 2 , and then dried under the conditions of 0.005 MPa and a temperature of 45°C to obtain a pretreated base paper, and the water content percentage of the pretreated base paper is 7%;

[0107] Step (2) Preparation of thermoplastic melamine glue: By parts, 1300 parts of 37% formaldehyde aqueous solution is mixed with 100 parts of ammonia water, and the pH is adjusted to 9. When the reaction temperature rises to 50°C, 200 parts of melamine is added and stirred for 10 minutes. Then, 400 parts of urea is added, heated to 65°C, and kept warm and evaporated until the water mass percentage is 25%. When the temperature is lowered to 40°C, 80 parts of diethylene glycol is added, and the temperature is further lowered to 35°C. Subsequently, 25% of the total mass of hydroxyacrylate-silicone copolymer is added, and after stirring evenly, a thermoplastic melamine glue with a density of 1.2 g / cm 3 is obtained;

[0108] Step (3) Impregnation: Impregnate the pretreated base paper with thermoplastic melamine glue. The impregnated paper first passes through the back coating roller, and the air is discharged by the breathing roller with an arc to filter the liquid. Then, the excess glue is wiped off by the metering roller and dried in a seven-section oven. The temperature of the first section of the oven is 110 °C, the temperature of the second section of the oven is 125 °C, the temperature of the third section of the oven is 135 °C, the temperature of the fourth section of the oven is 130 °C, the temperature of the fifth section of the oven is 130 °C, the temperature of the sixth section of the oven is 130 °C, and the temperature of the seventh section of the oven is 120 °C, so that the water content of the impregnated paper is 13%, and the glue application amount is 65 g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 25 °C by the roller water cooling method, sheared, stacked, paved, and hot-pressed to obtain the thermoplastic melamine glue-impregnated decorative paper.

[0109] The inspection methods and results are shown in Table 1.

[0110] Table 1

[0111]

[0112] Examples 1-5 have obvious performance improvements compared with Comparative Examples 1-9. It can be seen from Examples 4 and 5 that although the drying and cooling processes are different from those of Example 1, the performance is still better than that of Comparative Examples 1-9, indicating that these two conditions have a promoting effect on the performance rather than a decisive effect.

[0113] The difference between Comparative Example 1 and Example 1 is that the base paper was not pretreated, lacking the performance improvement brought by the modified nano-silica compared with Example 1.

[0114] The difference between Comparative Example 2 and Example 1 is that unmodified silica was selected. Due to the agglomeration of surface hydroxyl groups, it cannot effectively penetrate the fiber gaps, and there are no surface grafting groups to participate in the subsequent network construction. Instead, it acts as a defect point to cause stress concentration and significantly weakens the strengthening effect.

[0115] The difference between Comparative Example 3 and Example 1 is that conventional melamine glue was selected, lacking the flexible chain segment toughening of acrylic resin. The brittle cross-linked network is prone to generating and expanding microcracks when bent.

[0116] The difference between Comparative Example 4 and Example 1 is that the atmospheric drying in step (1) makes the modified nano-silica only adsorbed on the surface of the base paper and fails to form a mechanical interlock with the fibers, and it is easy to peel off from the interface under external force.

[0117] The difference between Comparative Example 5 and Example 1 is that the increase in the water content of the base paper dilutes the concentration of the impregnating glue, and the density of the cured resin film decreases. At the same time, the water catalyzes the side reaction of hot pressing to release formaldehyde.

[0118] The difference between Comparative Example 6 and Example 1 is that the acrylic resin is missing in the glue, and the rigid network of melamine lacks toughening and buffering, resulting in a sharp drop in the impact energy absorption capacity.

[0119] The difference between Comparative Example 7 and Example 1 is that the excessive acrylic resin occupies the crosslinking sites of melamine, inhibiting the formation of the three-dimensional network, and the density and strength decrease simultaneously.

[0120] The difference between Comparative Example 8 and Example 1 is that the premature addition of diethylene glycol triggers the side reaction of formaldehyde disproportionation, and the by-product formic acid catalyzes the formation of weak bonds such as methylene ether bonds, reducing the network stability.

[0121] The difference between Comparative Example 9 and Example 1 is that the low-temperature reaction causes the polycondensation of melamine to stay in the linear prepolymer stage, failing to form a highly branched crosslinked structure, and the overall performance deteriorates severely.

[0122] In summary, the realization of this solution is based on the combination of components and processes, and a single component and process cannot achieve the technical effects described in this solution.

Claims

1. A preparation method of a thermoplastic melamine glue-impregnated decorative paper, characterized in that, It includes the following steps: Step (1) Substrate pretreatment: Coat a modified nano-silica dispersion liquid on the surface of the substrate, with a coating amount of 8 - 12 g / m 2 , and then dry it under the conditions of 0.001 - 0.02 MPa and a temperature of 40 - 50 °C to obtain a pretreated substrate; Step (2) Preparation of thermoplastic melamine glue: By parts, mix 1200 - 1400 parts of formalin with 90 - 110 parts of ammonia water, adjust the pH to 8.8 - 9.

2. After the reaction temperature rises to 55 - 65 °C, add 180 - 220 parts of melamine, stir for 10 minutes, then add 380 - 420 parts of urea, heat to 83 - 90 °C, keep warm and evaporate until the mass percentage of water is 20% - 30%. When the temperature drops to 60 °C, add 70 - 90 parts of diethylene glycol, continue to cool to 30 - 40 °C, and then add 20% - 30% of the total mass of acrylic resin. After stirring evenly, thermoplastic melamine glue is obtained; Step (3) Glue dipping: Dip the pretreated base paper with thermoplastic melamine glue, dry, cool, shear, stack, lay, and hot press to obtain thermoplastic melamine glue - impregnated decorative paper.

2. The preparation method of the thermoplastic melamine glue-impregnated decorative paper according to claim 1, characterized in that, In step (1), the modified nano - silica dispersion includes: 5% - 10% of modified nano - silica by mass percentage, 1% - 3% of hydroxyethyl acrylate, 1% - 2% of acrylic acid, and the rest is water.

3. The preparation method of the thermoplastic melamine glue-impregnated decorative paper according to claim 1, wherein In the modified nano - silica dispersion, the modified nano - silica is acrylic - grafted nano - silica.

4. The preparation method of the thermoplastic melamine glue-impregnated decorative paper according to claim 1, characterized in that, In step (1), the water content percentage of the pretreated base paper is 6% - 8%.

5. The preparation method of the thermoplastic melamine glue-impregnated decorative paper according to claim 1, characterized in that, The density of the thermoplastic melamine glue is 1.0 - 1.3 g / cm 3 .

6. The preparation method of the thermoplastic melamine glue-impregnated decorative paper according to claim 1, characterized in that, In step (3), the process of dipping the pretreated base paper with thermoplastic melamine glue is as follows: The pretreated base paper first passes through the back - coating roller, then the excess glue is wiped off by the metering roller, passes through the drying oven, and the drying temperature is 110 - 135 °C to make the water content of the impregnated paper 12% - 15% and the sizing amount 60 - 70 g / cm², and then it is cooled.

7. The preparation method of the thermoplastic melamine glue-impregnated decorative paper according to claim 6, characterized in that, Before wiping off the excess glue with the metering roller, use a breathing roller with an arc to filter out air.

8. The preparation method of the thermoplastic melamine glue-impregnated decorative paper according to claim 1, characterized in that, In step (3), the drying method is drying in a seven - section oven. The temperature of the first section oven is 110 °C, the temperature of the second section oven is 125 °C, the temperature of the third section oven is 135 °C, the temperature of the fourth section oven is 130 °C, the temperature of the fifth section oven is 130 °C, the temperature of the sixth section oven is 130 °C, and the temperature of the seventh section oven is 120 °C.

9. The preparation method of the thermoplastic melamine glue-impregnated decorative paper according to claim 1, characterized in that, In step (3), the acrylic resin is a hydroxyacrylate - silicone copolymer.

10. The preparation method of the thermoplastic melamine glue-impregnated decorative paper according to claim 1, characterized in that, In step (3), the cooling method is to cool by blowing natural cold air through the oven, and then cool to the paper surface temperature of 25 - 30 °C by the water - cooling method of the roller.

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